Presently, display panels are more and more extensively applied. In particular, OLED (Organic Light Emitting Diode) display panels have been widely used in various display devices. In existing display panels, thin-film transistors are indispensable electronic devices. Taking a top-gate type thin-film transistor as an example, a buffer layer covers a light shielding layer, and an active layer is arranged in a region of the buffer layer corresponding to the light shielding layer. When the thin-film transistor is fabricated, it is necessary to provide a contact hole from which the light shielding layer is exposed for a dielectric layer and the buffer layer that are stacked and, then, a drain is connected to the light shielding layer through the contact hole.
However, the dielectric layer and the buffer layer are larger in thickness, and the dielectric layer and the buffer layer that are stacked are even larger in thickness, such that it is more difficult to provide the contact hole for the dielectric layer and the buffer layer that are stacked, and longer time is taken to do so. Therefore, photoresists are easily hardened in an etching process and, thus, are not easily to be removed, which has a negative effect on product yield.
It is to be noted that the above information disclosed in this Background section is only for enhancement of understanding of the background of the present disclosure and, therefore, it may contain information that does not form the related art that is already known to a person of ordinary skill in the art.